The formula to find the area of the segment is given below. It can also be found by calculating the area of the whole pie-shaped sector and subtracting the area of the isosceles triangle △ACB.

Formula for the area of a segment of a circle

where: C  is the central angle in DEGREES R  is the radius of the circle of which the segment is a part. π  is Pi, approximately 3.142 sin  is the trigonometry Sine function. See Trigonometry Overview

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Other circle topics

General

• Circle definition
• Parts of a circle (diagram)
• Semicircle definition
• Tangent
• Secant
• Chord
• Intersecting chords theorem
• Intersecting secant lengths theorem
• Intersecting secant angles theorem
• Radius of a circle
• Diameter of a circle
• Area of a circle
• Concentric circles
• Annulus
• Area of an annulus
• Sector of a circle
• Area of a circle sector
• Segment of a circle
• Area of a circle segment

Equations of a circle

• Basic Equation of a Circle (Center at origin)
• General Equation of a Circle (Center anywhere)
• Parametric Equation of a Circle

Angles in a circle

• Inscribed angle
• Central angle
• Central angle theorem

Arcs

• Arc
• Arc length
• Arc angle measure
• Adjacent arcs
• Major/minor arcs
• Intercepted Arc
• Sector of a circle
• Radius of an arc or segment, given height/width
• Sagitta - height of an arc or segment